The San Francisco-based improviser and sample manipulator is describing some of the more terrifying moments of his 1999 trip to war-weary Serbia. It wasn't a vacation -- Ostertag was in the Balkans performing his controversial Yugoslavia Suite, a multimedia piece rooted in the Serbian conflict and including computer-based war games and manipulated video footage.

That Ostertag would try to get into Belgrade at all was amazing enough -- read his diary of the harrowing tour in British mag The Wire -- but that he and his hot-wired laptops made it out in one piece was something of a miracle. Between crashing software and Serbs unimpressed with Ostertag's outsider perspective on their war, it was as smooth as a trip through the Balkans could be expected to be.

"I'm not sure whether I'd call touring Serbia a good experience," Ostertag laughs from home. "I'm glad I did it, and I've actually made very close friends in the Balkans as a result of the project, but it's something I never want to do again.

"The scariest moment of the whole thing came when we were on the train going into Serbia and the police approached us. They told us we had to go with them to the police station in Novi Sad and hauled us to the back of the train. I did not want to go to that police station.

"I don't think they were going to beat the hell out of us, and I really doubt that Milosevic would have made an incident out of some harmless avant-garde musician. But they could scare us for a while, and that's what they did."

Ostertag's current project is considerably less controversial and dangerous, but no less complex. Between Science And Garbage, which gets its world premiere Friday (April 13) at Innis Town Hall as part of the Images Festival, is a collaboration between Ostertag and Quebec animator Pierre Hébert.

The bizarre multimedia project features Hébert creating improvised animation on a computer program that Ostertag has designed while Ostertag himself draws on a digital drawing tablet and manipulates sound through the shapes he draws.

There's also a current affairs component, in which Ostertag and Hébert cut up sounds and pictures from the previous evening's local news. Ostertag promises that, in the spirit of pure improvisation, anything can happen.

A composer for most of his life, he says working with images has shifted his perspective.

"You have to think differently, because people respond so much more to images than sound. You can play a sound with really specific political and cultural connections and people will just shrug, but if you show them an image it really affects them.

"The Yugoslavia piece was really a lesson in that. The images I used in that piece could have caused riots. I'm not sure what we'll get from the news in Toronto, whether it'll be mayhem in the streets or a story on the dog-catcher. It's all usable, though."